Chromotype Permanent Photographs are a little unusual as they allow us to see how sepia photographs actually looked when they were first done, though they seem a little dark. As a process I dont quite understand how it was done. The photo and text are on the same sheet perhaps showing that the photo was a copy, perhaps by some photo-mechanical means.
What they did create was a glossy, clear, non-fading, 'plastic-looking' permanent photograph. With these, as you will see - the gold toning to make sepia has survived and is the colour sepia, whereas most carte de visite made of simple paper, albumen (egg white) and paper and gold toning - which with time and light breaks down to yellow - is hardly sepia at all!
The process was operated under licence as the process was copyright. The extra processing and paying for a licence made this expensive, and did increased the price, this does seems to have put people off from buying them.
The problem with these: the high gloss finish is prone to scratches and the film tends to curl and come away from the card mount

I have included a few that used what seems like a similar process - almost as good. These just reproduced the photograph and were pasted on to a standard back, note that there is even one created in Australia.

Robert Lansdale sent this information (May2004)

Information on the chromotype can be found in the Photographica World, the official journal of the Photographic
Collectors Club of Great Britain. Their issue No.91, Winter 1999/2000 has an elaborate article on The Carbon Process by Audrey Linkman of Manchester. The chromotype process is a carbon process with a few special kinks added by Claude Leon Lambert of Paris, France. He also developed the Lambertype process (enlarged image) and the Contretype process (positives for retouching and duplicating negatives).
He first came to attention in May 1874 in The Photographic News revealing his 'Lambertype'. By June 1875 Lambert had established a temporary studio in London. He toured England to sell licences for his patented processes.
Linkman does mention that Lambert used 'an interpreter' during demonstrations and later mentions 'the Lambert Brothers'. The Autotype company took over the patents while the Lamberts proceeded to America.
Thanks Robert - Roger Vaughan